1. Field of the Invention
This invention relates to an optical paper check device for a printer for detecting whether a paper is on the platen of the printer.
2. Description of the Prior Art
In a prior art printer, a mechanical paper check device has detected whether a paper is on the platen so as not to directly print on the platen. The mechanical device cannot accurately detect that the paper is on the platen because the detecting position of the paper changes depending on the stiffness of the paper. Thus use of an optical paper check device has been recently proposed. This optical paper check device determines whether a paper is on the platen by the change in reflectance of light spotted on the platen.
However, the paper check device erroneously detects that the paper is not on the platen when the reflectance at the sensed position of a paper is lower than elsewhere. This occurs, for example, when some dark patterns are printed on the paper.